Short-laser-pulse-driven emission of energetic ions into a solid target from a surface layer spalled by a laser prepulse

An efficient emission of picosecond bunches of energetic protons and carbon ions from a thin layer spalled from a organic solid by a laser prepulse is demonstrated numerically. We combine the molecular dynamics technique and multi-component collisional particle-in-cell method with plasma ionization to simulate the laser spallation and ejection of a thin (similar to 20-30 n m) solid layer from an organic target and its further interaction with an i ntense femtosecond laser pulse. In spite of its small thickness, a layer pr oduced by laser spallation efficiently absorbs ultrashort laser pulses with the generation of hot electrons that convert their energy to ion energy. T he efficiency of the conversion of the laser energy to ions can be as high as 20%, and 10% to MeV ions. A transient electrostatic field created betwee n the layer and surface of the target is up to 10 GV/cm.